I have to agree with the above post. From what I have seen, the routine things that most M.D.s do can be done well by many other healthcare workers.
Becoming technically competent at most procedures does not require a MD degree.
However, it is when presentations are not typical, in the unusual cases and situations that require a more detailed knowledge of concepts that a medical doctor comes into his/her own. That is the key difference in IMHO. Many may say that a CRNA is equal to an MDA but if you look at the difference in their education background (med school + residency vs. nursing school + working in ICU) there is a true fundamental difference.
Same goes for PA and MD. A PA attends trains for approx 18 months as opposed to 48 months + residency. A PA who has been around for awhile may have the the knowledge gained from experience that may make him/her comfortable managing most patients but that does not replace the fundamental base of knowledge of a medical doctor.
Just ask yourself who would you have perform anesthesia on your loved ones: A CRNA by his/herself or would you like a MDA around just in case things go wrong?
Optometrists place the title "Doctor" with their degree and call themselves "eye doctors" which tends to confuse the general public as many do not know the difference between OMD and optometrist. Optometrists take many of the same basic sciences med students do but they have no experience managing patients medically. In their clinical years, they practice in mostly a office setting. A OMD will have had 3rd/4th year in med school plus a whole year as med/transitional/surgery intern. Would you trust an optometrist to do vision correction (legal in one of the midwestern states) or other eye surgery on you or your family when they have never medically managed a patient? Even if the procedure itself is straight forward, I would never let an optometrist perform an invasive procedure on my eyes. The truth is many fields have non-MD personnel constantly trying to assume more legal rights to do what traditionally was reserved only for MD's. Each has their own organization that constantly fight in the political arena. For example In California, optometrist recently received prescribing rights after lobbying for it for many years. In fact one optometrist in California I know has received training to do Lasik procedures in that midwestern state mentioned above. Why? Because he believes that optometrists will be allowed to perform Lasik in California and other states in the near future! I don't know if that will ever happen but it reflects the mindset of some in these fields.
The truth is that one does not easily appreciate the limits of his/her own training without really knowing what MD training entails. I have known MDAs who were CRNAs earlier in their careers and my medicine resident was once a nurse. They have all told me the biggest difference was the level of understanding they had about the processes going on in their patients. They also said that they did not really appreciate this difference until they became MDs and were on the "other side".
Most of these non-MD personnel serve valuable functions in healthcare. Optometrists do a great job with refraction, picking up many eye disorders, and even detecting systemic diseases through evaluating the eyes. CRNA's and PA's help better utilize manpower with well trained people in patient care. The problem is when these people feel that they are functionally equivalent to MD'S.
The last thing I want to say is that CRNA's often site the fact that they were the ones who started administering anesthesia in this country and that MD's came onto the field later in the U.S. However, the field has become increasingly more complex and scientific the past 100 years. Patient safety has improved dramtically and many new significant contributions were made the last few decades since MDs entered anesthesia. Remember that barbers were some of the first ones to perform surgery...that does not mean they are the most qualified to do that in this day and age!
Sorry if I offended anyone. Please note that my sister-in-law is an optometrist and I am close friends with a CRNA and two PA's.